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Cubes of nylon sponge, cubes of polyurethane foam (PUF), cuttings of stainless steel sponges and the commercial carriers Kaldnes™ K1 were tested as inert supports for laccase production by the white-rot fungus Trametes pubescens under semi-solid-state fermentation conditions. The cultures operating with Kaldnes™ K1 led to the highest laccase activity (3667 U/l). In addition this support could be re-utilised, making the whole process more economical. Subsequently, the decolouration of simulated textile wastewater (STW) by T. pubescens grown on the different tested supports under semi-solid-state fermentation conditions was studied. Decolouration percentages around 66-80% were obtained in 96 h. It was found that STW decolouration was due to two mechanisms: laccase action (biodegradation) and adsorption onto fungal mycelium, save for the PUF cultures in which decolouration was mainly due to adsorption onto the support. Further, the decolouration of STW by Kaldnes™ K1 cultures in three successive batches of 96 h each was studied. Decolouration percentages of 51.3, 70.0 and 69.8%, were attained for each batch, respectively., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Laccase production by Trametes pubescens grown on sunflower-seed shells (SS) under solid-state fermentation (SFF) conditions in temporary immersion bioreactors was studied. Three immersion cycles were considered: 1 min immersed and 9 min non-immersed, 1 min immersed and 30 min non-immersed and 1 min immersed and 60 min non-immersed. The latter led to the highest laccase activities (4000-6000 Ul(-1)). Also, the in vitro and in vivo decolouration of the recalcitrant textile dye Remazol Brilliant Blue R (RBBR) was assessed. It was found that RBBR (133.33 mg l(-1)) was efficiently decolourised by T. pubencens grown on SS under SSF conditions in temporary immersion bioreactors in five successive batches. The percentage of RBBR decolouration was higher than 55% in 4h and around 70% in 24h in all the batches. However, it was found that RBBR decolouration by the crude culture filtrates was more advantageous. Thus, an RBBR decolouration percentage of nearly 80% in 2h was obtained., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Response surface methodology (RSM) was applied to optimise the decolouration of the diazo dye Reactive Black 5 (RB5) by crude laccase from the white-rot fungus Trametes pubescens. The presence of the redox mediator 1-hydroxybenzotriazole (HBT) greatly improved the decolouration levels of RB5 by crude laccase from T. pubescens. Central composite design (CCD) using RSM with three variables namely redox mediator (HBT), dye (RB5) and enzyme (laccase) concentrations was used in this study to optimise significant correlation between the effects of these variables on the decolouration of RB5. The optimum concentrations of HBT, RB5 and laccase were 1.17 mM, 150 mg/l and 500 U/l, respectively, for a maximum decolouration of RB5 (about 60% in 20 min). A quadratic model was obtained for dye decolouration through this design. The experimental values were in good agreement with the predicted ones and the model was highly significant, the correlation coefficient being 0.965. Interaction between HBT and RB5 concentrations, HBT and laccase concentrations and RB5 and laccase concentrations were negligible. In addition, when the kinetic parameters for RB5 decolouration were calculated according to Hannes-Wolf plot, the following values were obtained: K(M) of 260.11 mg/l and V(max) 37.59 mg/l min.

In this paper the efficiency of the combined action of laccase and cellobiose dehydrogenase (CDH) to decolourise different synthetic dyes such as Remazol Brilliant Blue R (RBBR), Methyl Green (MG), Direct Violet (DV), Ponceau Xylidine (PX), Bismark Brown (BB) and Poly R-478 (PR) was assessed. It was found that the use of CDH could be a promising alternative to the utilisation of the expensive and poisonous chemical mediators such as HOBT although much research on this topic remains still to be done.

In this paper the production of laccase and the decolouration of the recalcitrant diazo dye Reactive Black 5 (RB5) by the white-rot fungus Trametes pubescens immobilised on stainless steel sponges in a fixed-bed reactor were studied. Laccase production was increased by 10-fold in the presence of RB5 and reached a maximum value of 1025U/l. Enhanced laccase production in the presence of RB5 in this fungus is an added advantage during biodegradation of RB5-containing effluents. The decolouration of RB5 was due to two processes: dye adsorption onto the fungal mycelium and dye degradation by the laccase enzymes produced by the fungus. RB5 decolouration was performed during four successive batches obtaining high decolouration percentages (74%, 43% and 52% in 24h for the first, third and four batch, respectively) without addition of redox mediators. Also, the in vitro decolouration of RB5 by the concentrated culture extract, containing mainly laccase, produced in the above bioreactor was studied. The decolouration percentages obtained were considerably lower (around 20% in 24h) than that attained with the whole culture.